Disposable test strips are frequently used in personal blood glucose monitors for measuring blood glucose in daily life. Test strips are typically sensitive to outside elements, in particular humidity, that may compromise measuring accuracy after long-time exposure. Therefore, during long periods of storage, the test strips must be protected from outside elements, air humidity, in particular.
Traditionally, test strips have been stored in closeable plastic vials containing, for example, 25 to 50 strips. Such vials are not easy to use as they are separate components from the meter itself, resulting in more operations and hassle needed for performing a single blood glucose measurement. An exemplary vial is disclosed in WO 03/082092.
U.S. Pat. No. 6,908,008 discloses a test device with means for storing and dispensing test strips. The test strips are stored stacked within the device and pushed out by means of a slider.
Test strips may also be stored in cartridges (also cassettes, magazines) which are filled with test strips and placed into the monitor device. Some cartridges contain means for sealing each strip individually in a separate locker of the cartridge in a foil. Such cartridges are, however, expensive and difficult to manufacture. In addition, their dimensions are relatively large because of the individual lockers, resulting in bulky integrated monitors. Thus, they are not well suitable for small blood glucose monitors designed for frequently repeated measurements in everyday life.
Examples of commercially available test strip cartridges include Bayer Ascensia Breeze and Roche Accu-Chek Compact Plus. In patent literature, stacked test trip cartridges or the like devices have been disclosed, for example, in, WO 03/042691, U.S. Pat. No. 6,908,008, EP 1314029, CA 2583563.
Another type of cartridges (in addition to individually sealed strips) are cartridges that seal all strips inside the cartridge. This cartridge type removes the need for individual sealing. Typically the strips are stored in stacks. General problems associated with sealed cartridge-type solutions for stacked strips include wearing of seals, complex mechanisms needed for closing seals and, in particular, that the mechanism for pushing out the test strips one by one is inadequately sealed. Even if the strip exit port is sealed, the device typically requires an actuator inside the cassette to push out the strips. This actuator, if operated by the device, therefore needs to enter the cassette at some location. Needless to say, such mechanism should also be hermetically sealed in order to achieve a fully sealed container.
WO 2006/044850 discloses an exemplary sealed test strip cartridge for stacked test strips. The housing of the cartridge may be sealed for inhibiting introducing moisture into the interior of the housing by a rubber seal in the opening for test strips. A rubber seal as disclosed in the publication does not, however, ensure tight sealing as such, in particular, after many repetitions of strip dispensing. In particular, the force keeping the rubber parts together, and thus sealing the cartridge, may not be sufficient or may weaken during use. The cartridge comprises an integral plunger or slide mechanism for pushing test strips out of the cartridge, significantly increasing the costs of the cartridge. Because of this, the cartridge cannot be used as a disposable cartridge. Furthermore, the publication fails to present an effective method for sealing the plunger or slide mechanism.
Further, WO 2006/002432 discloses a cartridge comprising stacked sensor strips and sealable openings on opposite sides of the cartridge for bringing the sensor strips out of the cartridge one by one. In the case of electrochemical sensor strips, the strips are read by pushing them entirely out of the cartridge and by contacting them individually with external electrical contacts arranged in a sensor-dispensing instrument. In this solution the strip will need to be pushed entirely out of the cartridge to allow its reading. This results to significant space requirements and increases the dimensions of the sensor dispensing device.